Bifurcation honeycomb sandwich structure with optimized doubler

Abstract

A method of shaping a metallic honeycomb panel using a continuous drive sheet. The metallic honeycomb panel may have a perforated upper sheet, a non-perforated lower sheet, and a metal honeycomb core fixed between the upper and lower sheets. The method may include the steps of designing and manufacturing the drive sheet using finite element analysis (FEA) and criteria regarding shaping of the metallic honeycomb panel, then welding the drive sheet to the lower face of the lower sheet. The drive sheet may cover all of the lower face of the lower sheet and may have varying thicknesses determined based on the criteria and the FEA. The method may also include the steps of heating the drive sheet and metallic honeycomb panel to a creep forming or hot-stretch forming temperature and urging the metallic honeycomb panel and drive sheet into a male or female die mold to be shaped.

Having thus described various embodiments of the invention, what is claimed as new and desired to be protected by Letters Patent includes the following: 
     
       1. A method of shaping a metallic honeycomb panel having an upper sheet, a lower sheet with opposing upper and lower faces, and a metal honeycomb core fixed between the upper and lower sheets, the method comprising:
 welding a sacrificial drive sheet to the lower face of the lower sheet, wherein the drive sheet is sized and shaped to cover an entire area of the lower face of the lower sheet, wherein the drive sheet has at least one portion having a first thickness and at least another portion having a second thickness different from the first thickness; 
 heating the drive sheet and metallic honeycomb panel to a creep forming or hot-stretch forming temperature; 
 urging the metallic honeycomb panel and drive sheet into a male or female die mold; 
 cooling and the metallic honeycomb panel and the drive sheet; and 
 cutting the welded drive sheet off of the metallic honeycomb panel. 
 
     
     
       2. The method of  claim 1  further comprising attaching tooling to the drive sheet after the step of welding the drive sheet to the lower sheet; and stretching the drive sheet while urging the drive sheet into the die mold. 
     
     
       3. The method of  claim 1 , wherein the metallic honeycomb panel is made of Ti-Beta 21s titanium. 
     
     
       4. The method of  claim 1 , wherein the drive sheet is made of Ti-6242 titanium. 
     
     
       5. The method of  claim 1 , further comprising the steps of designing the shape and dimensions of the drive sheet using finite element analysis (FEA) based on characteristics related to shaping of the metallic honeycomb panel. 
     
     
       6. The method of  claim 5 , wherein the characteristics related to shaping of the metallic honeycomb panel include at least one of: material properties of the metallic honeycomb panel or the drive sheet, a degree of curvature to be imposed on the metallic honeycomb panel via the die mold, thickness of the metallic honeycomb panel, dimensions or spacing of the honeycomb core cells, upper sheet dimensions and characteristics, lower sheet dimensions and characteristics, the die mold's shape, and the die mold's dimensions, and amount of pressurization or heat to be applied during creep forming or hot forming of the metallic honeycomb panel. 
     
     
       7. The method of  claim 1 , wherein the first portion of the drive sheet contacts the lower sheet of the metallic honeycomb panel and the second portion of the drive sheet extends laterally outward from the first portion, beyond edges of the lower sheet, wherein the first thickness is thinner than the second thickness. 
     
     
       8. A method of shaping a metallic honeycomb panel having an upper sheet, a lower sheet with opposing upper and lower faces, and a metal honeycomb core fixed between the upper and lower sheets, the method comprising:
 receiving criteria regarding shaping the metallic honeycomb panel; 
 using the criteria to design shapes and dimensions of a continuous sacrificial drive sheet; 
 manufacturing the drive sheet according to the designed shapes and dimensions; 
 welding the drive sheet to the lower face of the lower sheet, wherein the drive sheet is sized and shaped to cover and contact all of the lower face of the lower sheet, wherein the drive sheet has at least one portion having a first thickness and at least another portion having a second thickness different from the first thickness; 
 heating the drive sheet and metallic honeycomb panel to a creep forming or hot-stretch forming temperature; and 
 urging the metallic honeycomb panel and drive sheet into a male or female die mold using an induced pressure differential or mechanical force. 
 
     
     
       9. The method of  claim 8 , further comprising clamping opposing ends of the drive sheet extending outward of the welded-on lower face, after the step of welding the drive sheet to the lower sheet; and stretching the drive sheet while urging the drive sheet into the die mold. 
     
     
       10. The method of  claim 8 , wherein the metallic honeycomb panel is made of Ti-Beta 21s titanium. 
     
     
       11. The method of  claim 8 , wherein the drive sheet is made of Ti-6242 titanium. 
     
     
       12. The method of  claim 8 , further comprising the steps of cooling the drive sheet and metallic honeycomb panel and cutting the welded drive sheet off of the metallic honeycomb panel. 
     
     
       13. The method of  claim 8 , wherein the step of using the criteria to design the shapes and dimensions of the drive sheet is performed via a computing device using finite element analysis (FEA), wherein the criteria includes characteristics related to shaping of the metallic honeycomb panel. 
     
     
       14. The method of  claim 13 , wherein the characteristics related to shaping of the metallic honeycomb panel include at least one of: material properties of the metallic honeycomb panel or the drive sheet, a degree of curvature to be imposed on the metallic honeycomb panel via the die mold, thickness of the metallic honeycomb panel, dimensions or spacing of the honeycomb core cells, upper sheet dimensions and characteristics, lower sheet dimensions and characteristics, the die mold's shape, and the die mold's dimensions, and amount of pressurization or heat to be applied during creep forming or hot forming of the metallic honeycomb panel. 
     
     
       15. The method of  claim 8 , wherein the first portion of the drive sheet contacts the lower sheet of the metallic honeycomb panel and the second portion of the drive sheet extends laterally outward from the first portion, beyond edges of the lower sheet, wherein the first thickness is thinner than the second thickness. 
     
     
       16. The method of  claim 8 , wherein the metallic honeycomb panel is a bifurcation panel configured for forming a portion of an inner acoustic wall of an aircraft engine nacelle. 
     
     
       17. A method of shaping an aircraft nacelle's titanium bifurcation panel, the bifurcation panel having a perforated upper sheet, a non-perforated lower sheet with opposing upper and lower faces, and a metal honeycomb core fixed between the upper and lower sheets, the method comprising:
 receiving, with a computing device, criteria regarding shaping the bifurcation panel; 
 designing shapes and dimensions of a continuous sacrificial drive sheet on the computing device using finite element analysis (FEA) and the criteria; 
 manufacturing the drive sheet according to the designed shapes and dimensions; 
 welding the drive sheet to the lower face of the lower sheet, wherein the drive sheet is sized and shaped to cover and contact all of the lower face of the lower sheet, wherein the drive sheet has varying thicknesses determined based on the criteria and the FEA; 
 heating the drive sheet and metallic honeycomb panel to a creep forming or hot-stretch forming temperature; 
 attaching clamps at opposing ends of the drive sheet extending outward of the welded-on lower face; 
 stretching the drive sheet via actuation of the clamps in opposing directions; and 
 urging the metallic honeycomb panel and drive sheet into a Male or female die mold using an induced pressure differential or mechanical force; 
 cooling the drive sheet and bifurcation panel; and 
 cutting the welded drive sheet off of the bifurcation panel. 
 
     
     
       18. The method of  claim 17 , wherein the criteria regarding shaping the bifurcation panel include at least one of: material properties of the bifurcation panel or the drive sheet, a degree of curvature to be imposed on the bifurcation panel via the die mold, thickness of the bifurcation panel, dimensions or spacing of the honeycomb core cells, upper sheet dimensions and characteristics, lower sheet dimensions and characteristics, the die mold's shape, and the die mold's dimensions, and amount of pressurization or heat to be applied during creep forming or hot forming of the bifurcation panel. 
     
     
       19. The method of  claim 17 , wherein the metallic honeycomb panel is made of Ti-Beta 21s titanium and the drive sheet is made of Ti-6242 titanium.